Why is Lubrication Oil Necessary?

Why is Engine Lubrication Necessary?

The largest use of lubricants is to lubricate the parts in internal combustion engines. The lubricating oil is pumped between the moving parts, forming a thin oil film, which coats and protects the moving parts from directly touching other moving parts. The piston ring traveling at approximately 65 miles per hour up and down the cylinder wall is separated from the cylinder wall by a thin, invisible lubricating film approximately 3 microns in depth. Without the oil film, the rapidly moving piston ring will make direct contact against the cylinder wall, causing extreme heat and friction, as it scrapes and drags against the cylinder wall. Catastrophic engine failure will result within a few minutes without an oil film separating the piston ring from the cylinder wall.

Seizing the Engine -- Can the Engine Operate Without Lubricating Oil?

No. In normal engine operation the bare metal surface of the piston ring never touches the bare metal surface of the cylinder wall. A micro-thin oil film prevents the moving parts from coming in contact with each other. Without this vital oil film, a rapid, catastrophic sequence results -- the engine’s piston rings will begin to score against the cylinder wall, causing a mass of aluminum, iron, and other metals to quickly form, which forces the piston rings into their groves, thereby allowing the combustion pressure to dissipate without pressing down the cylinder and the loss of engine compression. The loss of compression and the heavy drag caused by the badly scored parts scrapping against each other results in an immediate loss of power. This is referred to as “seizing the engine.” Repair of a seized engine is costly. It requires either a major engine rebuild or replacing the engine.

Why Do Engine Oils Need to be Changed?

There factors impact the useful life of lubricating oil:

First, if an external fluid contamination enters the oil it must be replaced immediately. Examples of external fluid contaminants are engine coolants, gasoline, diesel fuel, and water. For example, if water enters the lubricating oil, the water will quickly deplete the additives pack, accelerate the rate of oxidation, and render the lubricating oil ineffective. External fluid contamination is rare but when it does occur, the oil must be changed immediately.

Second, when the oil chemistry is degraded, the oil must be changed. Over time, the oil chemistry will degrade, resulting in abnormally high or low viscosity and high levels of oxidation. The additive pack, the chemicals added to the base oil in modern lubricating oils, is designed to be depleted over time. The rate of additive depletion can be abnormally accelerated by the presence of external fluid contaminations, such as water or fuel, and by the solid particle contaminants, especially if the particles are catalytic metals.

Third, particle contamination builds up, which causes the engine to wear more quickly. As the engine wears, the various metals used to build the engine, iron, aluminum, etc., form wear metals in the oil. These wear metals create an abrasive microgrit slurry of hard particles, which are recycled continuously back between the moving parts creating more wear metals, which are recycled, accelerating the rate of wear. Catalytic particles cause the additives to deplete as the engine operates. The higher the level of wear metals and abrasive particles, especially catalytic metals, the more quickly the engine wears and the more quickly the additive pack is depleted.